Numerical modeling of HgCdTe solidification: Effects of phase diagram, double-diffusion convection and microgravity level

A numerical model of HgCdTe solidification was implemented using finite the element code FIDAP. Model verification was done using both experimental data and numerical test problems. The model was used to evaluate possible effects of double-diffusion convection in molten material, and microgravity level on concentration distribution in the solidified HgCdTe. Particular attention was paid to incorporation of HgCdTe phase diagram. It was found, that below a critical microgravity amplitude, the maximum convective velocity in the melt appears virtually independent on the microgravity vector orientation. Good agreement between predicted interface shape and an interface obtained experimentally by quenching was achieved. The results of numerical modeling are presented in the form of video film

Evaluation of Temperature Gradient in Advanced Automated Directional Solidification Furnace (AADSF) by Numerical Simulation

A numerical model of heat transfer using combined conduction, radiation and convection in AADSF was used to evaluate temperature gradients in the vicinity of the crystal/melt interface for variety of hot and cold zone set point temperatures specifically for the growth of mercury cadmium telluride (MCT). Reverse usage of hot and cold zones was simulated to aid the choice of proper orientation of crystal/melt interface regarding residual acceleration vector without actual change of furnace location on board the orbiter. It appears that an additional booster heater will be extremely helpful to ensure desired temperature gradient when hot and cold zones are reversed. Further efforts are required to investigate advantages/disadvantages of symmetrical furnace design (i.e. with similar length of hot and cold zones)

Numerical Modeling of HgCdTe Solidification: Effects of Phase Diagram, Double-Diffusion Convection and Microgravity Level

Melt convection, along with species diffusion and segregation on the solidification interface are the primary factors responsible for species redistribution during HgCdTe crystal growth from the melt. As no direct information about convection velocity is available, numerical modeling is a logical approach to estimate convection. Furthermore influence of microgravity level, double-diffusion and material properties should be taken into account. In the present study, HgCdTe is considered as a binary alloy with melting temperature available from a phase diagram. The numerical model of convection and solidification of binary alloy is based on the general equations of heat and mass transfer in two-dimensional region. Mathematical modeling of binary alloy solidification is still a challenging numericial problem. A Rigorous mathematical approach to this problem is available only when convection is not considered at all. The proposed numerical model was developed using the finite element code FIDAP. In the present study, the numerical model is used to consider thermal, solutal convection and a double diffusion source of mass transport

Modeling the interaction of convex solidifying interfaces with spherical particles

The phenomenon of pushing during solidification is modeled for the case of particles producing a convex interface. The thermal and fluid fields generated by the particle melt solid system are calculated in a decoupled way determining in the first place the shape of the interface and then, the two main forces acting during pushing; the drag and repulsion forces. The thermal and fluid flow fields were calculated using finite element methods. Both, the drag and repulsion forces are integrated at each step and compared until both are equal and the steady state of pushing is reached. The repulsion force is integrated using the Casimir-Lifshitz Van der Waals interaction. The model predicts the equilibrium distance in a steady state of pushing for spherical particles and a convex solidifying interface. It is shown that the equilibrium separation distance for a convex interface results in a larger solidification velocity for trapping with respect to an ideal planar interface. The model results were in good agreement with experimental results for the critical velocity reported in the literature.Fil: Agaliotis, Eliana Mabel. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Grupo de Materiales, Modelización y Metrología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; ArgentinaFil: Rosenberger, Mario Roberto. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Grupo de Materiales, Modelización y Metrología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; ArgentinaFil: Ares, Alicia Esther. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Grupo de Materiales, Modelización y Metrología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; ArgentinaFil: Schvezov, Carlos Enrique. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Grupo de Materiales, Modelización y Metrología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; Argentin